A type of endoprosthesis device, commonly referred to as a stent, may be placed or implanted within a vein, artery or other tubular body organ for treating occlusions, stenoses, or aneurysms of a vessel by reinforcing the wall of the vessel or by expanding the vessel. Stents have been used to treat dissections in blood vessel walls caused by balloon angioplasty of the coronary arteries as well as peripheral arteries and to improve angioplasty results by preventing elastic recoil and remodeling of the vessel wall. Two randomized multicenter trials have recently shown a lower restenosis rate in stent treated coronary arteries compared with balloon angioplasty alone (Serruys, P W et al., New England Journal of Medicine 331: 489-495 (1994) and Fischman, D L et al. New England Journal of Medicine 331:496-501 (1994)). Stents have been successfully implanted in the urinary tract, the bile duct, the esophagus and the tracheo-bronchial tree to reinforce those body organs, as well as implanted into the neurovascular, peripheral vascular, coronary, cardiac, and renal systems, among others. The term “stent” as used in this application is a device which is intraluminally implanted within bodily vessels to reinforce collapsing, dissected, partially occluded, weakened, diseased or abnormally dilated or small segments of a vessel wall.
One of the drawbacks of conventional stents is that they are generally produced in a straight tubular configuration. The use of such stents to treat diseased vessels at or near a bifurcation (branch point) of a vessel may create a risk of compromising the degree of patency of the main vessel and/or its branches, or the bifurcation point and also limits the ability to insert a branch stent into the side branch if the result of treatment of the main, or main, vessel is suboptimal. Suboptimal results may occur as a result of several mechanisms, such as displacing diseased tissue, plaque shifting, vessel spasm, dissection with or without intimal flaps, thrombosis, and embolism.
As described in related U.S. patent application Ser. No. 08/744,002 filed Nov. 4, 1996 (now abandoned), Ser. No. 09/007,265 filed Jan. 14, 1998, now issued as U.S. Pat. No. 6,210,429, Ser. No. 08/935,383 filed Sep. 23, 1997 (now abandoned), 60/088,301 filed Jun. 5, 1998 (now expired), and PCT Patent Application No. PCT/US99/00835 filed Jan. 13, 1999, published under Publication Number WO99/36002 on Jul. 22, 1999, systems have been developed for deploying a main stent in a main vessel at the intersection of a main vessel and a branch vessel. Further, a branch stent may be positioned within a branch vessel through a side opening in the main stent. As will be appreciated, such tasks may be challenging.
For example, management of two guidewires used in introducing and/or orienting stents can pose particular challenges, such as the tendency of the guidewires to twist together. As another example, imaging placement of the stents using low-cost and convenient techniques, such as x-ray or ultrasound imaging, can be difficult using existing methods.